Heretofore, compact discs having a relatively large standard diameter (e.g., 12 cm), in which a number of pieces of music are recorded, have been generally used. However, recently, as CD players are becoming more and more popular, discs having a standard diameter which is smaller than that described above (e.g., 8 cm), in which 2 or 3 pieces of music are recorded, are more widely used. Therefore, it is desirable that a CD player be capable of playing discs having a large diameter and discs having a small diameter.
Heretofore, to play discs having different diameters on a disc player having a single disc insertion opening, an adapter 1 as shown in FIG. 10 is used. In this adapter 1, a base circular plate 2 is formed so as to have the same diameter as that of a disc having a large diameter. Plate 2 has elastic supporting arms 3 at several positions which can be extended to be opened. A disc (S) having a small diameter is clamped at a central portion of the adapter 1 by means of clamping protrusions 4 disposed on the supporting arms 3. By inserting this adapter 1 in the CD player through the insertion opening, it is possible to securely clamp the disc (S) having the small diameter on a turntable by using the periphery of the base circular plate 2 as a reference.
In some cases, when the disc having a small diameter mounted on the adapter 1 by the conventional techniques described above is inserted in the typical CD player through the insertion opening, a cut groove portion 3a existing between the supporting arm 3 and the base circular plate 2 in the adapter 1 passes an optical detecting means for detecting the insertion of the disc in the course of the disc loading. Groove 3a is formed in order that the supporting arm 3 can be elastically extended to be opened. As the groove 3a passes the optical detecting means, an erroneous detection by the detecting means may take place and the disc loading operation is stopped, which gives rise to a problem that the disc is not loaded at a predetermined position or that it cannot be ejected.
Further, in the case where a typical user believes that a disc having the small diameter can be used without an adapter and inserts a disc having the small diameter through the insertion opening, it is not possible to eject the disc.
Furthermore, for a CD player used on a vehicle, the use of the adapter 1 indicated in FIG. 10 is relatively complicated.